This section provides background information related to the present disclosure which is not necessarily prior art.
Dosimeters using optically stimulated luminescent (OSL) sensors with metal filters to continuously accumulate information on photon and neutron doses are well known and widely used. Examples of OSL based dosimeters are disclosed in these publications: M. S. Akselrod and S. W. S. McKeever, A Radiation Dosimetry Method Using Pulsed Optically Stimulated Luminescence, Radiat. Prot. Dosim., v. 81, No 3, 167-176 (1999). Mittani, J. C. R., Silva, A. A. R. d., Vanhavere, F., Akselrod, M. S., Yukihara, E. G., 2007; and Investigation of neutron converters for production of optically stimulated luminescence (OSL) neutron dosimeters using A1203:C. Nucl. Instr. Meth. Phys. Res. B 260, 663-671 (2007), and the following patents: U.S. Pat. Nos. 5,892,234, Method for Determining an Unknown Absorbed Dose of Radiation Using Optically Stimulated Luminescence; U.S. Pat. No. 5,962,857, Method for the Fast Determination of an Unknown Absorbed Dose of Radiation with High Sensitivity Using Optically Stimulated Luminescence; U.S. Pat. No. 8,921,795 on Method and Apparatus for Fast Determination of Unknown Dose; and U.S. Pat. No. 9,000,381, Method and Apparatus for Fast Determination of Unknown Dose. The disclosures of all of which are incorporated herein by reference in their entireties.
Likewise dosimeters using fluorescent nuclear track detector (FNTD) sensors to continuously accumulate information on photon and neutron doses and to measure low and high doses of neutrons and high doses of photons, are also well-known and widely accepted. Examples of FNTD based dosimeters are disclosed in these publications: G. M. Akselrod, M. S. Akselrod, E. R. Benton, and N. Yasuda, A Novel Al2O3 Fluorescent Nuclear Track Detector for Heavy Charged Particles and Neutrons, NIM B, 247 296-306 (2006); and 10. M. S. Akselrod, G. J Sykora Fluorescent Nuclear Track Detector technology—a new way to do passive solid state dosimetry, Radiat. Meas., 46 1671-1679 (2011); and the following patents: U.S. Pat. Nos. 7,141,804 Detection of Neutrons and Heavy Charged Particles; U.S. Pat. No. 7,902,525, Method of Luminescent Solid State Dosimetry Of Mixed Radiations; U.S. Pat. No. 7,943,911, Method of Luminescent Solid State Dosimetry of Mixed Radiations; and U.S. Pat. No. 7,964,854, Method Of Luminescent Solid State Dosimetry Of Mixed Radiations. The disclosures of all of which are incorporated herein by reference in their entireties.
However, OSL sensors and FNTD sensors are passive integrating dosimetry techniques, meaning that the sensors must be taken out of service and “read” with an external reader. While they provide sensitivity over a broad range, and a high degree of accuracy, these sensors typically cannot provide an immediate indication of the absorbed dose, and thus they cannot not provide an alarm capability that “active dosimeters” like semiconductor detectors or gas counters can do. However, active dosimeters typically have very limited dose and dose rate ranges, limiting their application to low doses. Moreover, active dosimeters stop acquiring data if the circuit fails or loses power, meaning that dose history can be lost. Because active sensors typically require a lot of power, the risk of shut down and loss of data can be significant.